1. Field of the Invention
The invention pertains to the field of computer graphics. More particularly, the present invention relates to a method of generating a sequence of triangles from a vertex raster with and without half resolution edges while decompressing a compressed geometry stream.
2. Description of the Related Art
Rendering images in modem computer graphics is a highly computationally intensive task. Indeed, the capabilities of modem graphics processors and the ever-increasing expectations of the public have both created and fueled the need for more detailed, realistic and complex renderings. Graphics processors typically contain at least two sections: a geometry section and a rasterizing section. The geometry section carries out the floating-point calculations to calculate the size, position and orientation of three-dimensional triangles, which are drawing primitives used in computer graphics. The three-dimensional triangles computed by the geometry section are then projected and rasterized onto the display device in two dimensions by the rasterizing section.
For realistic renderings, a number of characteristics must be specified for each constituent triangle of an object to be displayed. These characteristics allow highly detailed images having complex textures to be rendered on the display screen. Generating such detailed images and complex textures requires a large amount of storage to save and compute the characteristics during the rendering process. Also, a substantial amount of time is required to process these characteristics. What is needed, therefore, is a method of reducing the amount of memory needed to generate the triangles required to render such graphic images. What is also needed is a method that reduces the number of memory operations that are required to accomplish this goal, thus reducing the processing time required.
When rendering graphic images, it is often necessary to display textures of higher resolution next to textures of relatively lower resolution. The textures, therefore, must be adjusted accordingly, to allow a seamless transition between local areas of differing resolutions. What is also needed, therefore, is a method for efficiently manipulating the textures making up a graphic image to allow for regions of lower resolution to be rendered next to regions of relatively higher resolution.
Triangles may be specified in terms of their constituent vertices, three such vertices making up a triangle. These vertices, each representing texture values, may be sent to the geometry section as a compressed data stream that is called a compressed geometry stream, in the manner described in commonly assigned U.S. patent application Ser. No. 08/511,294, entitled "Compression Of Three Dimensional Graphics Data Using A Generalized Triangle Mesh Format", by Michael F. Deering, filed on Aug. 4, 1995, the disclosure of which is incorporated herewith in its entirety by reference.
Therefore, what is needed is a method of efficiently converting the compressed geometry stream into a sequence of triangles with or without lower resolution regions for texturing larger triangles, while simultaneously decompressing the geometry stream.